Nudibranchia is a celebration of the wild variety of physical and behavioral traits that have evolved in this order of animals. Nudibranchs are mollusks without shells: “nudi” = naked and “branch” = gill. The 206 species here are just a small portion of those known: estimates of the total number of species run from 3,000 to 6,000. Given how vast the oceans are, how short a time we humans have been able to physically explore under- water, and how small a percentage of the 7/10’s of Earth’s total area has been visited, who knows? The oceans are the last great frontier on the planet. Nudibranchs inhabit every part of every ocean: from shallow reefs and mudflats to the depth of a thermal vent, from the Arctic to the equator. These creatures are short lived. Many have only a few days to a few months to reproduce once they reach sexual maturity. In order to maximize their chances of finding each other, all are hermaphrodites. They can also mate across generations, in what is called protandry (making a baby with your grandfather or great niece): any sexually mature nudibranch can mate with any other mature one of its species, regardless of size. Penile and vaginal structural variation in nudibranchs is truly stupefying and wondrous. A wide array of mimicries and camouflages has also evolved among nudibranchs. Some slugs’ cerata look so much like their prey species that the slugs are virtually invisible if nestled amongst them. Many can swim.